The gist of the bug is described at http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=525186
In a nutshell, the 'other' option (used for specifying a new folder for searching) is gone from the 'Folder' pull-down. It seems to be present in other gtk applications (e.g., sound-juicer).
Although it doesn't look like there's much difference between the debian 0.9 and the sourceforge repository, I went ahead and built regexxer from the svn code... the 'other' option is missing with the 'Folder' pull-down with the svn version as well...
That's a known problem. It turns out to be a GtkFileChooser bug:
http://bugzilla.gnome.org/show_bug.cgi?id=579958
I'll keep this bug open until the GTK+ bug is resolved.
It's a gtk+ bug: http://bugzilla.gnome.org/show_bug.cgi?id=579958